I have gone through your query and understood your concerns. From your symptoms I can tell you some possible causes which are hyper pigmentation and fixed drug eruption
due to some drug used recently or addison's disease. I suggets you to consult dermatologist
to rule out the above possible causes and if they are ruled out you must check your ACTH
levels to rule out addisons disease.It is difficult to diagnose your case without examination so consult your dermatologist and follow his instructions accordingly. Thank you.